Moderation of growth and sucrose flux in sugarcane by temperature.
Sugarcane plants (cultivar NCo376) were studied to assess the effects of temperature and season (spring and autumn equinox) on the morphological and physiological response of stalk components. Plants were grown from single-eyed setts for ca. five months and then placed into three temperature controlled glasshouses (22/12°C (C), 27/17°C (W) and 32/22°C (H) day/night temperatures). The plants were sampled twice weekly over a one month period., and intemodes 4, 6 and 10 of the primary haulms of each plant sampled for growth and sugar analysis. During spring, the leaf emergence rates were 0.0303, 0.1095 and 0.1682 leaves d(-1) at temperatures C, W and H, respectively; and 0.0327, 0.0824 and 0.113 leaves d(-1) in autumn. The phyllochron intervals were 114°Cd in spring and 147°Cd in autumn. Highest green leaf blade area of the primary haulms was achieved at H (438.0 and 511.7 cm2 in spring and autumn, respectively). The stalk extension rates were 1.22, 1.02, 0.38 cm d(-1) (spring) and 1.35, 0.98, 0.45 cm d(-1) (autumn), respectively, in descending order of temperature. Total biomass and stalk biomass per plant were not affected by temperature, despite the differences in stem elongation. Internodes of plants at C were shorter but thicker and heavier than the comparable internodes of plants at W and H. In autumn, the mature internode sucrose concentrations were 35.5, 29.2 and 25.5% at C, W and H, respectively; corresponding to mean RS% of 5.7, 9.8 and 13.3%, and fibre % of 58.8, 61.1 and 61.3%, at the respective ascending order of temperature. Sucrose % in the mature internodes in spring were 27.8, 20.9 and 19.9% at C, W and H, respectively; corresponding to RS% of 5.9, 9.76 and 10.9% and fibre % of 66.3, 69.4 and 69.2% at the respective ascending order of temperature. Temperature effect on the concentration of the stalk components of the immature internodes was in general not significant. Sucrose partitioning coefficients in the mature internodes were 0.25, 0.21 and 0.20 in spring and 0.50, 0.32 and 0.21 in autumn (at C, W and H, respectively). Data that resulted from this study, which is isolated to temperature and cultivar NCo376 can be used in models of sugarcane that simulate leaf appearance and senescence, assimilate partitioning between leaf and stalk and assimilate partitioning between the stalk components namely sucrose, reducing sugars and fibre.